Hydraulic dredging system and method for collecting and removing material from deep sea beds

ABSTRACT

Hydraulic dredging system and method, more particularly for great depths, constituted by a first ship carrying the vertical material removing tube, by connection devices giving possibilities for inclining the tube about its fixing point on the ship, a collecting unit which collects the materials from the bottom of the sea and inserts them in the vertical material removing tube and a second ship providing the towing of the collecting device by use of a cable fitted with a device for lifting that device.

United States Patent 11 1 Condolios 1 1 Sept. 30, 1975 1 1 HYDRAULIC DREDGING SYSTEM AND METHOD FOR COLLECTING AND REMOVING MATERIAL FROM DEEP SEA BEDS [75] Inventor: Elie Condolios, Grenoble, France [73] Assignee: Societe Generale de Constructions Electriques et Mecaniques (ALSTHOM), Grenoble, France [22] Filed: June 22, 1973 [21] Appl. No.: 372,516

[30] Foreign Application Priority Data June 22, 1972 France 72.23440 [52] US. Cl. 37/58; 37/72; 37/195; 37/D1G. 8 [51] Int. Cl. E02F 3/88 [58] Field of Seareh.... 37/54, 58, 61, 62, 72, 37/D1G. 8, 195; 299/8, 9; 114/50, 51; 61/72.3

156] References Cited UNITED STATES PATENTS 1,643.2-17 9/1927 LaGrangc 114/51 3,226,854 1/1966 Mero 37/58 3,2481% 1 2 5/1966 Gardner. .lr..

$310,894 3/1967 Ball 3.429.062 2/1969 Nelson 3,456,371 7/1969 Graham et a1. 37/61 X 3.522.670 8/1970 Flipse et a1. 37/D1G. 8 3,588,174 6/1971 Rossfelder 299/8 Primary Evuminer-Clifford D. C rowder Attorney, Agent, or FirmCraig & Antonelli l 5 7 ABSTRACT Hydraulic dredging system and method, more particularly for great depths, constituted by a first ship carrying the vertical material removing tube, by connection devices giving possibilities for inclining the tube about its fixing point on the ship, a collecting unit which collects the materials from the bottom of the sea and inserts them in the vertical material removing tube and a second ship providing the towing of the collecting device by use of a cable fitted with a device for lifting that device.

8 Claims, 8 Drawing Figures US. Patent Sept. 30,1975 Sheet 1 of 4 3,908,290

US. Patent Sept. 3001975 Sheet 2 of4 3,908,290

FIG.2

US. Patent Sept. 30,1975 Sheet 3 of4 3,908,290 I US. Patent Sept. 30,1975 Sheet4 0154 3,908,290

FIG-.8

HYDRAULIC DREDGING SYSTEM AND METHOD FOR COLLECTING AND REMOVING MATERIAL FROM DEEP SEA BEDS The present invention relates to hydraulic dredging installations for collecting and removing materials vertically at a high solid flow rate, more particularly for great depths. One application of the invention will be the hydraulic collecting and vertical removing of polymetallic nodules found on deep sea beds.

The system which is the object of the invention consists in separating the functions of the various elements 7 of the system so as to obtain maximum efficiency in collecting and vetically removing the nodules from the sea bed to the surface, having a maximum system using time and means for rapid operation on the various elements of the system and more particularly on the collecting device on the sea bed, in order to impart very great reliability to the installations.

The solution according to the invention consists in the use of two ships at the surface.

The first ship, called the mining ship having a suitable shape for towing the tube, providing power for the pumping device for vertically removing the dredged nodules, the storing of the nodules, and the pumping of these nodules towards the ore ships.

The second service ship enables the collecting device to be towed, on the sea bed, the vertical removing tube to be suitably positioned, rapid operation on the collecting device in the case of obstruction of the tube, and the collecting device to be raised in the case of repair or replacing.

In that solution, the flexibility of the tube is such that the collecting device is practically independent from the mining ship. Only the operation of the two ships, according to the condition of the sea, enables the path of the tube which is the most favorable to the conditions for vertical removing of the nodules to be obtained.

That relative independence of the collecting device in relation to the mining ship affords two great advantages: It enables the best technical and economic conditions to be obtained for collecting the nodules on the sea bed by means of correct positioning of the collecting device on the sea bed; and it enables rapid operation on the collecting device in the case of an incident with the device or the vertical removing system.

Indeed, the collecting device and the vertical removing system are subject, during use, to various hazards which may limit the operation time of the system, which may make the operating of such a system impractical from an economic point of view.

The main hazards encountered are: (l) Fouling of a natural or artificial obstacle, placed on the sea bed, by the collecting device; (2) admission of too great a quantity of solid materials in the vertical removal tube, which may lead to the stoppage of the vertical removing and the obstruction of the tube; (3) obstruction of the tube due to stoppage of the pump in the case of a power cut; (4) faulty operation of the collecting system and of the system for the removal of the clay collected on the sea bed and of the nodules to be vertically removed; and (5) breakdowns of all sorts occurring in the collecting device, requiring the repairing or replacing thereof which cannot be effected on the sea bed.

According to the invention, the dredging installation constituted by the mining ship carrying the vertical removing tube and, possibly, a tower fitted with the pumping devices offers the possibility of inclining the tube around the fixing point on the mining ship.

That particularly affords the advantage of being able to raise the collecting device, the vertical removal tube and, possibly, the tower, towards the surface of the sea, due to the means installed on the service ship which normally provides for the towing of the collecting device.

The arrangement of the ships also enables the partial raising of the collecting device to be effected very rapidly, to carry out, for example, the unblocking of the vertical removing tube in the case of blocking of that tube by materials being used, for example, by the simple increase in the distance between the two ships, playing on the flexibility of the vertical removing tube and, if applicable, on the possibility of inclining its fixing point on the ship.

Partial raising enables either the dredging device to be cleared from an obstacle or the vertical removing tube to be emptied on the sea bed if a plug forms inside it subsequent to too great a concentration of materials. To effect that emptying of the tube, it is sufficient to stop the pumping system after the raising of the collecting device.

Rapid operation is particularly important, in the first case, to avoid the breakdown of the collecting device and, in the second case, to avoid the forming of too great a plug, which it would be difficult to clear.

In the case of a breakdown of the collecting device, the complete raising of the latter will be effected by winding the towing cable on a winch installed on board the service ship, without making any modification or effecting any dismantling of the vertical removing tube, but playing on its flexibility and on its possiblity of inclination about its fixing point on the ship.

It is then possible to raise the collecting device rapidly without reverting to complex dismantling operations. The advantages as a whole afforded by the invention enable, more particularly, the stopping periods to be reduced and hence, the production of nodules dredged by the system to be increased appreciably.

The mining ship will, according to the invention, have, for its main functions: (1) The directing of the dredging operations as a whole, that is, the measuring and controlling of the general data required for coordinating the movements of the main elements of the installation; (2) the supplying of power and propulsion means for the mining ship and rigid tube as a whole; (3) the supplying of the required power to the pumping system; (4) the storing of the materials vertically removed from the sea bed in wells or hoppers provided for that purpose; and (5) the further handling of the materials stored and the transporting thereof to the ore ships.

One of the solutions for transmitting power to the vertical substance removing column consists in the use of a tower containing dredging pumps as stated in French Pat. No. 2,041,311 and its certificate of Addition No. 2,043,460 which French patents correspond to US. Pat. No. 3,693,272 In that case, the dredging tower which is connected on the one hand to the mining boat at its upper part and on the other hand, to the rigid tube by its lower part will, according to the invention, have the functions of: (l) Placing the dredging pumps at a certain depth in relation to the surface to enable, by means of the counterpressure obtained, the cavitation of the pumps to be avoided during suction at a great depth; (2) enabling the conveying water to be separated from the materials at the bottom of the tower; and (3) vertically removing the materials from the bottom of the tower to the surface by conventional means.

Such a tower is connected to the mining ship by a device articulated so as to enable it to be independent of the rolling and pitching movements of the ship to which it is connected. It can have, at judiciously selected points, propulsion means which will enable it to be propelled at a speed almost equivalent to that of the ore ship and to keep, during dredging, a position which is almost vertical.

The hydraulic vertical removing tube will have, according to the invention, the function of routing and conveying the materials to be dredged from the sea to the mining ship or to the foot of the tower. That tube, whose dimensions will be chosen according to the solid material flow rate and the sort of materials to be con veyed, will be of two different types: Rigid, in the upper part, at is connection with the ship or the tower; or flexible or articulated in its lower part (the last ten or so meters) at its connection with the collecting device.

The tube, connected rigidly to the ship or to the tower at its upper part, will be moved in the liquid element by propulsion means installed on the ship (and, if applicable, on the tower). That tube will be lightened or weighted down at particular points to obtain, when the installation is in motion, a path which departs as little as possible from the vertical.

That tube may bear the cables or pipes which may transmit data or energy coming from or going to the collecting deivce which shall be called a dredging bucket in the following description. The end of the rigid tube on the sea bed will be connected to an articulated or flexible tube connecting it to the dredging bucket so that the said dredging bucket may follow the configuration of the sea bed and absorb the variations in depth of the sea. The dredging bucket on the sea bed will be intended for gathering the materials to be dredged and inserting them after washing, if applicable, into the vertical removing tube. It will be towed in front by a cable drawn by a vessel known as the service ship in front of the mining ship, in a dredging axis determined by the mining ship, according to the conditions of swell and currents. The speed of that ship will be the same as that of the mining ship, so as to obtain an advancing of the dredging bucket at the same speed as the latter.

An auxiliary cable will provide the connection between the towing cable and the lower end of the tube above the flexible tube, so as not to pull the latter taut during the towing of the dredging bucket and to allow it all the required flexibility for absorbing the changes in level of the sea bed.

The dredging bucket on the sea bed will be fitted with a suitable detection device enabling the mining ship to situate its position inasmuch as concerns the plane and the depth with respect to itself and to the service ship to make it possible to obtain its correct position on the sea bed and in the intended dredging axis.

The service ship will have for its function, on the one hand, the towing of the dredging bucket on the sea bed in'the intended dredging axis, by a cable which connects it to the dredging bucket, and the directing of the latter in the required direction, a operation which is difficult to effect if the movement of the dredging bucket is effected simply by the mining ship through the vertical removing tube, for the latter is subjected by the sea currents to twisting and bending phenomena.

This towing arrangement moreover, enables the dredging bucket to be placed, during use, substantially been described at the beginning of this text. This dredging installation has, among other particularities, that of bringing all its equipment towards the dredging site on the mining ship and the service ship; of positioning its equipment itself to effect the dredging work such as described previously; and of enabling the dismantling of the equipment in a way which makes it possible to return to the part for the maintenance thereof without outside power means.

For that secondary mission, according to the invention, the mining ship will have the possibility of storing on board the rigid vertical removing tube; and the possibility of uncoupling the tower from its coupling connection to tow it at the stern in the horizontal position by means of cables provided for that purpose. Such an arrangement enables good maneuverability of the mining ship and of the tower when in motion.

The mining ship will also have the possibility of assembling or dismantling the rigid vertical removing tube.

The tower will have the possibility, by means of ballasts, weights and a closing device, provided for that purpose, of becoming uncoupled from the mining ship, of floating on the surface of the sea in the horizontal position and the possibility of coming into that position will enable the rigid tube to be assembled or dismantled and to be assembled again on the mining ship.

The service ship will have the possibility of storing on board the articulated or flexible tube, storing on board the collecting dredge bucket; and raising to assist the implementing or assembling or dismantling of the tubes.

Two hydraulic deep water dredging installations for implementing the method according to the invention will be given by way of examples hereafter, with reference to the accompanying drawings, wherein:

FIG. 1 is a general diagrammatic view of an installation according to the invention, during use;

FIG. 2 is a diagrammatic view of the installation at the beginning of the raising of the dredging bucket;

FIG. 3 is a diagrammatic view of the installation towards the end of the raising of the dredging bucket;

FIG. 4 is a diagrammatic view of the installation at the end of the raising of the dredging bucket;

FIG. 5 is a diagrammatic view of the installation at the beginning of the hydraulic tube raising operation;

FIG. 6 is a diagrammatic view of the installation during the raising of the tube;

FIG. 7 is a diagrammatic view of the installation at the end of the raising of the tube; and

FIG. 8 is a diagrammatic view of a variant of the installation.

The diagrammatic FIGS. 2, 3, 4, 5, 6, and 7 are not to scale inasmuch as concerns the distances between the ships and the dredging depth, so that the curves of the cable 6 and of the tube 3 do not correspond to reality.

In FIG. 1 it will be seen a deep-water dredging installation comprising the mining ship 1 at the bottom of which is fixed, by an articulation system enabling the inclining thereof, a tower 2 in the bottom of which are placed lift pumps to produce upstream thereof a counter-pressure suitable for preventing cavitations when suction at great depths is effected, such as described in the above-mentioned French patents and their corresponding US. Pat. No. 3,693,272.

The tower 2 is provided with suitable closing means and may be uncoupled from the mining ship and then be set afloat, at the surface of the sea in the horizontal position, by means of ballasts and weights. The hydraulic tube 3 starts from the bottom of that tower and ends up at the dredging bucket 4, such as that described in U.S. Pat. No. 3,829,160, situated on the sea bed, the lower part 5 of the tube being constituted by articulated elements in order to give it great flexibility to enable the dredging bucket to follow the configuration of the bottom.

The tube 3 may be lightened, as, for a great dredging depth, its weight would be too great, It would then be weighted at 9 to impart thereto, when the installation is in movement, a path which is near to vertical.

The dredging bucket 4 is towed along the bottom, in normal use, by means of a cable 6 pulled by a tug ship 7. A cable 8 ensures the connection between the tow cable 6 and the rigid part 3 of the tube, above its articulated part 5 in order to leave the latter all the required flexibility for absorbing the changes in level of the sea bed.

That dredge bucket towing arrangement makes it possible to utilize a hydraulic vertical removal tube 3 without any deformations and a substantially vertical orientation. this considerably reducing the losses of head in that tube and, consequently, the power required for vertically removing the materials.

The dredged materials are transferred from the mining ship 1 to the transport ship 10 by means of a hydraulic tube 11.

The rapid partial raising operations on the dredging bucket 4 in the case Where an obstacle is encountered, or to empty rapidly the vertical removing tube 3 on the sea bed in the case of forming ofa plug of materials, are effected simply by an increase in the distance between the ships 1 and 7.

The complete raising operations on the dredging bucket become apparent in the following figures.

In FIG. 2 is seen the tug ship 7, which comprises a winch l6 enabling the winding and the raising of the tow cable 6 and consequently of the dredging bucket 4, the assembly formed by the towing cable 6, the dredging bucket 4 and the tube 3 assuming, at the beginning of the raising operations, the position shown in that figure.

FIG. 3 shows the position of that assembly formed by the cable, the dredging bucket and the tube towards the end of the raising operations, where it is seen that the dredging tower 2, articulated at its fixing point at the bottom of the mining ship 1 assumes an inclined position enabling it to follow the inclination of the tube.

FIG. 4 shows the dredging bucket 4 in the completely raised position, ready to be lifted onto the ship by a crane in order for maintenance to be effected thereon.

The raising operations on the hydraulic tube are shown in FIGS. 5, 6, and 7.

The first operation consists in uncoupling the dredging tower 2 from the bottom of the ship to bring it behind the ship, in the vertical position shown in FIG. 5, where the tug ship 7 begins to raise the cable 6.

The tug ship then maneuvers to place itself in the current behind the ship, in the position shown in FIG. 6.

It then raises the cable 6; the dredging bucket 4 is removed and it moves away from the mining ship to position the suitably weighted tower 2 and the tube 3, as shown in FIG. 7, so that the dismantling of the tube and of the tower may then be effected.

FIG. 8 shows a variant of an installation in which the vertical removing tube 3 is connected directly to the mining ship by means of an oscillating connection 12, such as a pivoting connection, the vertical removing of the materials in the tube 3 then being effected by the known air lift system, by means of a pump 14 injecting air under pressure through a tube 13 connected suitably at 15 to the upper part of the vertical removing tube 3.

While I have shown and described several embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to a person skilled in the art, and I therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are obvious to one of ordinary skill in the art.

What is claimed is:

1. A hyraulic dredging installation for collecting and vertically removing materials at a high solid flow rate, particularly at great depth, from the floor of the sea, comprising a first ship for receiving said materials, a material removing tube pivotally connected to said first ship and extending substantially vertically therefrom to the floor of the sea, material collecting means disposed on the floor of the sea and connected to said material removing tube for gathering materials from the sea bed and inserting them into said tube, a second ship for towing said material collecting means, a tow cable extending from said second ship and being directly connected to said material collecting means on said floor of the sea and means for increasing the distance between said first and second ships such that said second ship effects at least partial raising of said material collecting means by the direct connection thereby during movement of said second ship.

2. An installation as defined in claim 1 wherein said material collecting tube is substantially rigid over its length and has a first portion connected to said material collecting means which is flexible.

3. An installation as defined in claim 2 wherein said material collecting tube has a second portion between said first portion and the much larger remainder of the tube which is heavier than other parts of the tube.

4. An installation as defined in claim 3 wherein an auxiliary towing cable is connected between the portion of said towing cable adjacent said material collecting means and a rigid portion of said material collecting tube.

5. An installation as defined in claim 4 wherein said auxiliary towing cable is connected to said second portion of said material collecting tube.

7 8 6. An installation as defined in claim 1, wherein said in the case of an obstruction of said material colmeans for raising further includes winch means on said lecting tube by moving the towing ship to effect an second ship and connected to said tow cable. increase of the distance between said towing ship 7. A method for collecting and vertically removing and the material receiving ship such that the direct materials at a high solid flow rate, particularly at great connection of said towing ship to said material coldepth, from the floor of the sea, using a towing ship, a lecting devices effects at least partial raising of said material receiving ship, a material collecting device at material collecting device during moving of said the floor of the sea and a mate ial collecting tube extowing ship. tending from the material collecting device to the ma- 8. A method as defined in claim 7, further including terial receiving ship, comprising the steps of 10 the step of maintaining said material collecting tube at towing the material collecting device from the towing proper disposition for conveying material by maintainship by directly connecting said material collecting ing a prescribed distance between said towing ship and device to said towing ship, and said material receiving ship. 1 at least partially raising the material collecting device I g 

1. A hyraulic dredging installation for collecting and vertically removing materials at a high solid flow rate, particularly at great depth, from the floor of the sea, comprising a first ship for receiving said materials, a material removing tube pivotally connected to said first ship and extending substantially vertically therefrom to the floor of the sea, material collecting means disposed on the floor of the sea and connected to said material removing tube for gathering materials from the sea bed and inserting them into said tube, a second ship for towing said material collecting means, a tow cable extending from said second ship and being directly connected to said material collecting means on said floor of the sea and means for increasing the distance between said first and second ships such that said second ship effects at least partial raising of said material collecting means by the direct connection thereby during movement of said second ship.
 2. An installation as defined in claim 1 wherein said material collecting tube is substantially rigid over its length and has a first portion connected to said material collecting means which is flexible.
 3. An installation as defined in claim 2 wherein said material collecting tube has a second portion between said first portion and the much larger remainder of the tube which is heavier than other parts of the tube.
 4. An installation as defined in claim 3 wherein an auxiliary towing cable is connected between the portion of said towing cable adjacent said material collecting means and a rigid portion of said material collecting tube.
 5. An installation as defined in claim 4 wherein said auxiliary towing cable is connected to said second portion of said material collecting tube.
 6. An installation as defined in claim 1, wherein said means for raising further includes winch means on said second ship and connected to said tow cable.
 7. A method for collecting and vertically removing materials at a high solid flow rate, particularly at great depth, from the floor of the sea, using a towing ship, a material receiving ship, a material collecting device at the floor of the sea and a material collecting tube extending from the material collecting device to the material receiving ship, comprising the steps of towing the material collecting device from the towing ship by directly connecting said material collecting device to said towing ship, and at least partially raising the material collecting device in the case of an obstruction of said material collecting tube by moving the towing ship to effect an increase of the distance between said towing ship and the material receiving ship such that the direct connection of said towing ship to said material collecting devices effects at least partial raising of said material collecting device during moving of said towing ship.
 8. A method as defined in claim 7, further including the step of maintaining said material collecting tube at proper disposition for conveying material by maintaining a prescribed distance between said towing ship and said material receiving ship. 